Cam follower



1961 J. DECKER 3,003,491

CAM FOLLOWER Filed March 23, 1960 2 Sheets-Sheet 1 INVENTOR. JACOB DECKER fli'TORNEYS Oct. 10, 1961 Filed March 23, 1960 J. DECKER CAM FOLLOWER 2 Sheets-Sheet 2 INVENTOR. JHCOB DECKER 8 MM 9 HTTOHNEYS United States Patent 3,003,491 CAM FOLLOWER Jacob Decker, Cincinnati, Ohio, assignor to The Cincinnati Milling Machine Co., Cincinnati, Ohio, a corporation of Ohio Filed Mar. 23, 1960, Ser. No. 17,108 2 Claims. (Cl. 125-11) The present invention relates to a tracing mechanism of the type using a cam and a cam follower and is particularly suited for control of a grinding wheel dressing unit.

In the present invention a cam has at least two straight segments which intersect at a corner to form an exterior angle greater than 180 degrees. A cam follower is pivotally attached to a forming member, such as a wheel dressing tool, and pivots about an axis. The follower has a flat surface, and the axis is substantially in this surface and preferably centered therein. The flat surface is held against the cam by a biasing force, the flat surface adjusting itself to the angle of the cam segment with which it is engaged, since the follower is pivotally mounted. The dressing tool to which the follower is mounted is laterally movable across the cam and is longitudinally movable in accordance with the cam conformation. Thus, as the cam follower moves across the cam in the dressing operation, the dressing tool follows a path defined by the cam segments. As the fiat surface of the follower slides toward a corner of the earn a substantial portion of the fiat surface remains in guided contact with a cam segment until the axis reaches the corner, at which time the cam follower pivots on the corner to swing another substantial portion of the fiat surface into guided contact with the next cam segment.

Thus, in the present invention, line contact of the cam follower with the cam, which would increase the pressure applied to the cam and promote wear, is avoided. Since line contact is avoided, small imperfections or irregularities in the cam segments do not cause corresponding irregular movements of the cam follower, and hence the dressing tool.

An object of this invention is to reduce wear of the cam and cam follower in a tracing mechanism.

Another object is to reduce the sensitivity of a tracing mechanism to small imperfections of the cam.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

In the drawings:

FIG. 1 is a view partly in cross-section, of a grinding wheel truing unit having a cam and cam follower controlling mechanism.

FIG. 2 is a fragmentary sectional view along a line 22 of FIG. 1.

FIG. 3 is a partial side elevation of the diamond points and grinding wheel shown from line 33 of FIG. 1.

As shown in FIG. 1, a grinding wheel is received in a wheel head housing 12 which includes an upper portion 14. Spaced transverse guide bars 16 are received in a recess in the upper portion 14. A carriage 18 having a transverse slide 20 received between guide bars 16 is movable in a straight path transverse to the grinding wheel on antifriction balls 22 caged betwen the guide bars 16 and the slide 20. A handwheel 24 is journaled in the upper housing portion 14 and is connected by conventional motion transmitting means (not shown) to slide 20 to move the carriage 18 transversely.

3,003,491 Patented Oct. 10, 1961 Mounted on carriage 18 are a pair of spaced vertical guide bars, one shown as 26. Received betwen the vertical guide bars 26 is a diamond bar housing 28 which has vertical ways 30 adjacent the guide bars 26. Housing 28 is movable vertically towards and away from the grinding wheel on balls 32 received between ways 30 and tracks 33 in the guide bars 26. Transverse movement of the carriage 18, together with the vertical movement of the diamond bar housing 23, makes that housing 28 movable universally in a plane.

A diamond bar 34 is mounted in a sleeve 36 which is secured in the diamond bar housing 28 and extends throu'gh an elongated transverse slot 37 in wheel head housing 12. As shown best in FIG. 3 the diamond bar has a pair of spaced diamond points 38, 40 extending therefrom, which form the wheel when moved across the grinding wheel cutting surfaces 42, 44.

As shown best in FIG. 2, cam 46 is mounted in a plane transverse to the grinding wheel on a bracket 48 attached to the upper portion 14 of the wheel head housing. The cam has cam surfaces comprising an initial cam surface 50, an intermediate cam surface '52, and a final cam surface 54. These surfaces are straight line segments which intersect at corners 56 and 58 to form exterior angles greater than degrees.

A follower housing 60 is attached to the top of sleeve 36, which extends above diamond bar housing 28, and has a bore 62 therein to receive annular bearings 64 through which a cam follower 66 is pivotally mounted for rotation about an axis 68. The follower 66 extends from the housing 60 and has a flat surface 76 in sliding contact with a cam surface, the flat surface '70 containing the axis 68 which is centrally located therein. A biasing force is supplied by a helical spring, represented in simplified form at 72, which is attached betwen two fixed points, one at the lower end of vertical guide bar 26 and the other at the top of diamond bar housing 28, the biasing force holding the follower 66 in contact with the cam 46.

In a truing operation, as the handwheel 24 is turned, the follower 66 moves along initial surface 50. The diamond bar 34 moves in a path parallel to this straight cam segment 50. During a portion of that movement one diamond point 38 is in forming contact with beveled side 42 of the grinding wheel. As the follower 66 approaches the corner 56, the one diamond point 38 becomes disengaged from the beveled side 42. When the follower is at the position A, a portion of the flat surface 70 still contacts the cam surface 56, and the axis 68 is still on the surface '50 side of the corner 56. The follower '66 continues to move across the cam 46 and, as the axis 68 passes the corner 56, the follower pivots and swings a portion of the flat surface 70 into engagement with the next surface 52 of the cam 46 for movement along that surface as indicated at B. Here again a substantial portion of the follower surface 7t) is in engagement with the cam 46.

The follower now moves across the second surface 52 and approaches the corner 58. During this time, neither of the diamond points is in contact with the grinding wheel 10. Corner 58 is negotiated by the follower in the same manner as corner 56, and the follower moves across the final surface 54. During this movement, the diamond bar 34 traces a path which brings the other diamond point 46 into forming contact with beveled side 44 of the grinding wheel.

The beveled sides 42 and 44 are now trued on the grinding wheel. The angle of the bevel is controlled by the action of follower 66 on cam 46 since the component of movement of the diamond bar toward and away from the grinding wheel is controlled by movement of the cam follower 66 on the surfaces of cam 46 during transverse movement of the diamond bar 34.

Because the follower 66 has a substantial portion of the flat surface 70 in contact with the cam except at the instant of pivoting around a corner, the resultant force holding the follower in engagement with the cam is spread over that portion of the flat surface. This reduces the pressure per unit of area of contact, thus reducing the wear between cam and follower since wear is proportional to pressure per unit of area of contact. Small areas of contact, such as line and point contact, are, for the most part, avoided. The area of contact does approach a line at the instant of pivoting at a corner, but the advantage of rolling motion is present.

The fiat surface of contact between cam and follower results in a smooth surface on the grinding Wheel beveled sides since the follower is not sensitive to small irregularities in the cam surface. This results in a trued grinding Wheel surface with fewer surface irregularities than may be on the surface which controls truing.

What is claimed is:

1. In a machine tool having a grinding wheel and a diamond bar movable transversely across the wheel in translation, the combination comprising a cam lying in a plane extending transversely relative to the wheel, said cam having a plurality of cam surfaces normal to said plane and intersecting to form at least one exterior angle greater than 180 degrees, a cam follower having a flat surface and pivotally mounted on said diamond bar for rotation about an axis normal to the plane of the cam, said axis lying centrally in said fiat surface, said fiat surface urged against the cam to define a resultant force acting through said axis to swing the fiat surface out of engagement with one cam surface and into engagement with the next cam surface as said axis passes the corner at the intersection of said cam surfaces during movement of the diamond bar across the wheel.

2. In a machine tool having a grinding wheel with beveled sides, a slide movable transversely relative to said wheel along a straight path, and a diamond bar having two diamond points extending outwardly on either side therefrom slidably mounted in the slide for movement towards and away from the grinding wheel, the combination comprising a cam lying in a plane and having one cam surface normal to said plane and parallel to said path, said cam also having an initial and a final cam surface normal to the plane of the cam and parallel to the beveled sides of the wheel, said initial and final cam surfaces intersecting said one cam surface at corners having exterior angles greater than degrees, a cam follower having a fiat surface and pivotally mounted on said diamond bar for rotation about an axis normal to the plane of the cam, said axis lying centrally in said flat surface, and biasing means to urge said fiat surface against said cam to guide one of said diamond points along one beveled side of the grinding wheel in forming contact therewith as the cam follower moves along said initial earn surface and to guide the other of said diamond points along the other beveled side of the wheel in forming contact therewith as the cam follower moves along said final surface during transverse movement of the slide, said biasing means defining a resultant force acting through said axis to swing the fiat surface out of engagement with one cam surface and into engagement with the next cam surface after approximately half of said fiat surface has passed a corner during transverse movement of the slide.

References Cited in the file of this patent UNITED STATES PATENTS 2,468,096 Miller Apr. 26, 1949 2,539,941 Allen Jan. 30, 1951 2,907,315 Hill Oct. 6, 1959 2,930,373 Jessup et al. Mar. 29, 1960 

